Here is the first part of the problem: -- there are two -different- formulas for antifreeze/coolant that are used in modern automobiles: - GM-spec Dexcool, or Zerex-spec G05.

Here's the second part of the problem:-- if you mix Dexcool and G05, you end up with a semi-solid gel that will destroy your cooling system.

So what is in the Mazda6 as delivered from the factory?
Mazda is not telling; Ford is not telling.
There are several threads on this board that speculate on what the factory fill is. None comes to a conclusion that inspires confidence.

If you need coolant, you can take your Mazda6 to the Mazda dealership, and they will refill it from the unmarked barrel of Mazda coolant.

But what if you want to top off your coolant yourself?
If it is Dexcool in there, adding G05 will turn your coolant to gel, and could cause engine damage.
If it is G05 in there, adding Dexcool will turn your coolant to gel, and could cause engine damage.

Whatever is in there, it is a good idea to flush and replace every couple of years. That is what we are going to do next week in our '04 which still has the original factory fill.

Our instructions to the (independent) repair shop:-- after flushing, fill with Zerex G05. The consensus seems to be that G05 has a slight edge over Dexcool.

Besides looking at a dealer in Omaha who looked at me like 'What do you mean, 'Do I have Mazda coolant for sale?' Guy looked like I asked for the holy grail....

I will likely go the standard Prestone route. If the anti-freeze is changed on a regular basis, there is zero benefit in using long-life fluid. I'd rather save a few bucks by going to Costco, knowing I'll replace it in (at mose) 2 years anyway. Prestone, distilled water and RedLine Water Wetter has never let me down. The Prestone has equally superior protection for dissimilar metals, and Water Wetter only adds to that protection, in addition to helping the water remove heat.

On my '06, Mazda specs FL22-compatible coolant/anti-freeze. I haven't researched enough to know which ones are FL22 compliant. Prestone or Peak, or one of the many other brands sells a "universal" pre-mixed coolant. They say you can add it to any color anti-freeze, any make/model. I haven't tried any of them yet, my coolant level is just slightly below the full mark, so no need to add. It would be better to just go back to the standard green stuff.

This document- from the State of Florida suggests that FL22 is a term unique to Mazda: the only coolant or antifreeze Florida lists that mentions "FL22" is the Mazda brand. Hey, when Mazda claims that the best FL22 coolant is Mazda FL22 coolant, who can argue?

Besides looking at a dealer in Omaha who looked at me like 'What do you mean, 'Do I have Mazda coolant for sale?' Guy looked like I asked for the holy grail....

I will likely go the standard Prestone route. If the anti-freeze is changed on a regular basis, there is zero benefit in using long-life fluid. I'd rather save a few bucks by going to Costco, knowing I'll replace it in (at mose) 2 years anyway. Prestone, distilled water and RedLine Water Wetter has never let me down. The Prestone has equally superior protection for dissimilar metals, and Water Wetter only adds to that protection, in addition to helping the water remove heat.[/b]

Probably the best solution as long as you completely flush out the old stuff, and most likely a lot cheaper and easier to obtain than the mysterious FL22.

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